Semiconductor Device Technology — DU B. Sc. (Hons) Electronics Previous Year Question Papers

4. a. Discuss the important properties of silicon oxide (SiOz) and explain why it is 6 widely used in semiconductor device technology. Explain wafer cleaning technology in semiconductor fabrication. Briefly describe 6 wet cleaning and dry cleaning techniques. c. Explain oxide quality, step coverage and P-glass (phosphosilicate glass) flow in 6 semiconductor fabrication. 5. a. Explain the process of thermal diffusion in semiconductors. Derive the diffusion 6 expression for a constant surface concentration and plot the resulting diffusion profile. b. Provide a detailed step-by-step account of the photolithographic process, starting 6 from wafer cleaning to the final stripping of the photoresist. C. Why is a "Clean Room" environment essential for lithography? Explain the 6 classification system (e.g., Class 10 vs. Class 100) and the specific types of contaminants that must be filtered out. Describe the mechanism of Sputtering for metal deposition. Discuss the role of inert gas (like Argon) and the advantages of sputtering in terms of "step coverage." What is BiCMOS technology? Explain the rationale behind integrating both Bipolar and CMOS devices on a single chip and the trade-offs involved in terms of fabrication cost. C. Outline the major process steps involved in fabricating a NMOS structure. Use a 6 neat cross-sectional diagram to show the sequence. 7. a. How are passive components like resisters and capacitors are fabricated in 6 b. Explain the process of Ion Implantation for dopin a semiconductor material. 6 Describe the steps and discuss parameters such as implantation range and channelling effects. C. Compare the structural fabrication complexities of Bipolar Junction Transistors 6 (BJT) and MOSFETs. Why is CMOS technology currently more dominant in digital logic than Bipolar technology?